#! /bin/bash
cp /etc/apt/sources.list /etc/apt/sources.list.bak

# ubuntu 20.04 LTS
echo deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse                > /etc/apt/sources.list         
echo deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse       >> /etc/apt/sources.list                 
echo deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse        >> /etc/apt/sources.list                 
echo deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse       >> /etc/apt/sources.list                 
echo deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse      >> /etc/apt/sources.list                 
# echo deb http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse > /etc/apt/sources.list
# echo deb http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse >> /etc/apt/sources.list
# echo deb http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse >> /etc/apt/sources.list
# echo deb http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse >> /etc/apt/sources.list

apt update